This invention relates to a method to determine the flatness σf a floor accord ng to the preamble of the first claim

The invention also relates to a measurement apparatus for measuring of the flatness of a floor according to the method according to the invention.

U is known to increase the usable surface in warehouses by making more intensive ¹ use of the height of a warehouse surface. Use is for instance made of fork-lift trucks with an increased reach in the height to place goods at increasingly higher levels. The height of such warehouses can for instance be up to 1θm, where conventional warehouses reach only up to a height of 10m. Such forMift trucks however require floors with a considerably higher fla ness than floors on which goods are not placed at such heights. An insufficiertly flat floor on such heights namely causes considerable movements of the loε>d, in particular, when the fork-lift truck, carrying the load at such a height mcves along the warehouses Such movements jeopardize the stability of the fory-lift trυck and may cause collisions wilh the storage means, often metal racKS, when the aisles between which the fork-lrft trucks move are very narrow There is therefore a need for floors with an increased flatness in order to meet tr-is use.

In ©rder to meet this need, it is necessary to measure and further record the flatness of existing floors In this context the following standards have for exaτιple been developed' the German DIN15185, the commercial recommendation TRT34 and the German standard N491.

US4689892 for example describes a measurement apparatus for measuπnp the flatness of a floor. The measurement apparatus measures thereto the d ⁱ fference between the floor and a reference surface, defined by a reference part of the apparatus, The reference part of US4689892 consists of a cart supported by four wheels and the reference surface is in this case defined by the surface of motion of the centre of gravity of the cart when the cart moves on the floor. Underneath the cart an inclinometer is provided, enclosed by two measunng wheels, which move over the floor when the cart moves along a measunng direction and execute dunng this motion, an ascending and descending movement, according to the difference between the floor and the reference surface. This movement is measured by the inclinometer and determines the flatness of the floor. The width of Hhe measuring wheels of the measurement apparatus, the measuring width, has however been deliberately limited, in order to increase the precision of the measurement as much as possible, by narrowing the measuring width.

The flatness measured by such a measurement apparatus and the behεviour derived therefrom of a fork-lift truck, driving on the floor, does however not correspond to the actual behaviour of a fork-lift truck, carrying loads at relatively high levels. It is as a consequence a problem of the easting measure nent apparatus that the measurement of the flatness of the flcor insufficiently represents the behaviour of a fork-lift truck, carrying these loads at relatively ^igh levels

It is therefore an object to provide a method and an apparatus, allowing to determine the flatness of a floor, with a better prediction of the behaviour of a vehicle, carrying a load at high levels

Tfrs object is reached according to the charactenzing part of the first claim.

Thereto, the method and measuring apparatus according to the present invention is charactenzed in that the measuring width corresponds to the contact width of a vehicle wheel.

The inventor has found that by determining the flatness of the floor from a measuring width as narrow as possible with the floor, it is not the flatness of the floor which is measured but rather the roughness or texture of the floor Although the roughness of the floor along with the flatness or me Tioor determine iot example the structure of the floor and thus determine the behaviour of vehicles which move on the floor, the roughness of the floor tends to focus on vibration or movement as the effect on the vehicle with a higher frequency rather dhan movements or vibrations of the vehicle caused by the flatness of the floor In order to take these effects into account when calculating the behaviou ^• of the vehicle on the floor, the measurement results of the measuring device can be processed so as to filter the high frequency vibrations from the resutts. Such an approach disregards the contact width of the vehicle wheel of the vehicle The inventor has found that this contact width is an important contributor to the behaviour of the vehicle on the floor and that this contact width must be taken into account when determining the flatness of the floor The inventor also has found surpnsingly that by substantially matching the measunng width to the contact width, a flatness which gives a better assessment of the behaviour of the vehicle on the floor can be measured.

Preferred embodiments of the method according to the present invention are characterised in that by moving the measuring apparatus along the measuring direction, according to the difference between the reference surface and the floor, a sensing element of the measunng element moves up and/or down relative to the reference section The size of the up- and/or downward movement of the sensing element relative to the reference surface if determined by measunng means of the sensing element, depending on the measured up- and/or downward movement of the measuring signal generation Such an aoproach has the advantage that small differences between ,he reference surface and the floor can be converted into a controlled motion o ^' a sensing element, the movement of the sensing element being easier and more accurate measurable than the differences between the reference surface and the floor.

Futher preferred embodiments of the method according to the present invention ¹ are charactensed in that by moving the measuring apparatus along the measuring direction a contact portion of the sensing element through two contact points, set up at a measunng width apart, contact the floor and with it movtfs the sensing element up and/or down in dependence on the difference between the floor and the reference surface. In preferred embodiments the contact points are provided to support the contact portion substantially or even entirely during the movement of the measurement apparatus along the measuring direction so as to further increase the accuracy of the measurement, tøy providing such contact portion, the differences between the reference surface and the floor can be measured. Indeed, by moving the contact section up and/or down on the floor when moving the measuring apparatus allong the measuring direction and measuring this movemer t, the flatness of the floor can be determined in a rather easy manner. By making use of contact points the risk decreases that local unevennesses that will only cause high-frequency vibrations, will be measured. The three contact points are further preferably laid out in a single line.

The contact points are generally respectively on opposite sides of tne contact port on of the measuring width where the contact portion of each rs mounted transverse, preferably perpendicular, to the measuring direction.

In further preferred embodiments the contact part contacts hrough three, ι//ith further preference exactly three, contact points, with the extreme contact points set up at the measuring width in contact with the floor as it was fourrd that an optimum was reached between finding a minimum contact width, RO as to avoid υndesired measurements^ and the best possible support to the contact section With the most preference is the distance between the contact points substantially 150mm or 150 mm.

According to preferred embodiments of the present invention, the vehicl* wheel is the wheel of a fork-lift truck. Fork-lift trucks are often used in applications where the flatness of the floor is important, as was explained above.

Preferably, the method is used for determining the flatness of a warehous ^e floor, since in these uses the flatness of the floor is important, as was discussed already above.

The invention also relates to a measuring apparatus for measuring the flatness of a floor according to the method of the present invention, comprising a reference section for a reference surface defined relative to a floor and a sensing element for scanning a measuring width along a measu ring direction and to provide a measurement signal generation corresponding to a difference between the floor and the reference surface, characterized in that the measuring width substantially corresponds to the width of contact a vehicle wheel

In prefered embodiments of the measuring apparatus accordint to the present invention, the measuring element includes a sensing element provided to move up and/or down relative to the reference section with the Movement of the measunng apparatus along the measuring direction according to the difference between the reference surface and the floor and measurement means provided to generate the measurement signal depending on the sι?e of the upward and/or downward movement of the sensing element relative to the reference surface, according to a preferred embodiment of the method according to the present invention explained above

In further preferred embodiments of the measuring apparatus according to the present invention the sensing element includes a contact part which is provided through two contact points, set up at the measuring wicrth, when moving the measunng apparatus along the measunng direction, to contact the floor and thsreby to move the sensing element up and/or down taking into dependence of the difference between the floor and the reference, accordmς to a preferred embodiment the method according to the present invention explained above

In further preferred embodiments according to the present invention the contact portion consists essentially of at least three, preferably exactly three, as explained above, measuring wheels mounted around an axle which prcvide the contact Such an executed contact portion is easily moved along the measuring direction. It is also possible to manufacture these wheels with a rac ius of a high accuracy, in order to be able to transform the up and/or downward motion with hngh accuracy into a difference between the floor and the reference surface. Preferably, the measunng wheels are narrow compared to the measuring width ir order to further reduce the risk that local irregularities affecting the measurement too much Narrow measuring wheels also push loose local irregularrties away when dπving the contact portion along the measuring direction which makes the measurement more accurate.

In further preferred embodiments according to the present invention the axle is set up in such a manner that it can only perform a substantially upwards and downwards movement, The inventor has found that such an 3xle allows to reduce the influence of local irregularities, particularly local depressions, such as pits in the floor, in order to obtain a better measurement.

In prefered embodiments of the measuring apparatus according to the present invention, the reference section includes a support part whicih is provided -o support the measuring apparatus with at least 3 support points on the floor while measuring the flatness of the floor. Such a support section is always easy to make and makes it also possible to define with sufficient precision the reference surface relative to the floor so as to measure the flatness of tihe floor with sufficient accuracy.

In further preferred embodiments of the measuring apparatus according to the preserw invention, the support section includes at least one supporting wheel for supporting the measuring apparatus. Such a structure offers the advantage thai moving the measurement apparatus according to the measuring direction is further simplified.

In further preferred embodiments of the measuring apparatus according to the present invention, the support section includes at least a first and a second axle of respectively a first and a second supporting wheel to support nhe measuring device. Such a structure offers the advantage that moving tΛe measurement apparatus according to the measuring direction is further simplified.

In further preferred embodiments of the measuring apparatus according to the present invention, the second axle is set up rotatably according to the first axle around a rotation axis substantially perpendicular to the firs- axle. Such an arrangement allows for the measuring apparatu s to be supportsd by four main support points, improving the stability of the apparatus and thus improving the accuracy of the measured differences between the floor and th? reference surface,

In further preferred embodiments of the measuring apparatus according to 'ϊhe present invention the first and second supporting wheel substantially has a contact width which essentially corresponds to the measuring width Such a structure offers the advantage that the reference surface aSso takes into sccount the contact width of vehicle wheels so that the applicability of the measured flatness of the floor using a similar approach further increases

The invention further relates to a method for flattening a floor where the flatness of the floor is determined by the method according to the present invention and the floor is subsequently flattened based on the measured flatness of the floor

Trvs invention will be further clarified on the basis of the description and the accompanying figures of preferred embodiments of the method and measunng apparatus according to the present invention

Figure 1 shows a view in perspective of the measunng apparatus according to the present invention

Fidυre 2 shows another view in perspective of the measuring apparatus shown in Figure 1

Figure 3 shows a side view of the measunng apparatus shown in Figure 1

Figure 4 shows a front view of the measunng apparatus shown in Figure 1.

Figure 5 shows a rear view of the measuring apparatus shown in Figure 1.

Figure 6 shows a top view of the measuring apparatus shown in Figure 1.

Figure 7 shows a bottom view of the measunng apparatus shown in Figure 1

Figure 8 shows a view in perspective of another embodiment of the measuring apparatus according to the present invention

Figure 9 shows another view in perspective of the measuring apparatus shown in Figure 8.

Figure 10 shows a side view of the measuring apparatus shown in Figure 8. Figure 11 shows a front view of the measuring apparatus shown in Figure 8.

Figure 12 shows a rear view of the measuring apparatus shown in Figure 8

Figure 13 shows a top view of the measuring apparatus shown in Figure 8.

Figure 14 shows a bottom view of the measuring apparatus shown in Figure 8.

The measuring apparatus 1 shown in Figures 1 and 8 is provided to measure to fhe flatness of a floor by the method according to the present iiwention. The measuring apparatus 1 thereto includes a reference section 2 and a measuring element 5,

Thfc reference section 2 defines a reference plane with respect to the floor which supports the measuring apparatus. The reference plane is an imaginary piane which is for instance defined by the movement plane in which the centre of gravity or another point of the measuring device 1 moves, b/ moving the reiference part 2 on the floor, usually along a measuring direction 3

The reference section 2 shown in Figures 1 and 8, includes a support section 10 which is provided to support with at least three support points 16, 17, T8 and/or 19 the measuring apparatus 1 on the floor while measuring the flalness of the floor. In figure 1 and 8, these support points are not collinear points At least one of the three support points 16, 17, 18 and/or 1θ in Figure 1 are located on a supporting wheel 11. The support section 1 D shown in Figjre 1 and 8 includes a first 13 and a second axle 14 provided Λfith respectively a first 11 and second supporting wheel 12 for rolling support of the measuring apparatus 1.

Such a realisation of the reference part 2 of the measuring apparatus is however not necessary for the measuring apparatus of the invention The measuring apparatus 1 can not, for example rest on the floor and the reference oart 2, for example, can be provided with conductors stretched above the ftøor for example lines such as ropes, cables, etc. provided to conduct the measuring element 5 along guides contact-free with the floor ^{, β} y using a support section 10 it was however found that a sufficiently accurate neasurement can be achieved in a simple way.

Although the support section 10 shown in Figures 1 and 8 comprises a supporting wheel 11 , this is not necessary for the invention and support section 10 may also for example comprise a surface for sliding across the floor Using at least cne supporting wheel 11 , however, it was found by the inventor tnat a much easier movement of the support section 10 on the floor can be achieved without significantly reducing the accuracy of measurement The advantage of the siiinple forward movement of the support section 10 on the floor is further enhanced by using at least two axles 13, 14 provided with the first a id second supporting wheel 11 , 12. These two supporting wheels 11 ,

12 provids preferably also at least three support points 16, 17, 18 to form a stable support wherein t^e second axle 14 is supported for example by two supports 16 and 17 and ¹ the first axle 13 by at least support point 18 Other configurailions are possible, of course, for example, wherein the second axle 14 is supported for example by two support points 16 and 17 and the first axle

13 by at least support pent 18

The first and second 13, 14 axle, as shown in Figure 1 , are provided with the first and second supporting wheel 11, 12 which extend along substantially the entire width of the support part 10 and consist of several smaller wheels around the respective axle 13, 14 This is not necessary for the invention and the first and second axle 13, 14, for example, can be piovided with each two wheels which are located respectively at the extremities of the axle 13, 14. It is possible to provide an axle with two such wheels to combine with another axle which in turn is provided with a wheel which extends substantially over the entire width of the axle

The first and second support wheel 11 , 12 which, as shown in Figure 1 and nn more detail in Figures 4, 5 and 7, extends over substantifilly the entire width of the respective first 13 and second 14 axle is made up of various sυb-ivheels, so as to allow a more simple structure of the support vuheels The distance between the wheels of the first and/or second supporting wheel 11 , 12 us preferably minimized and more preferably, are the sub-whee s substantially adjacent to each other, as shown in Figures 4, 5 and 7. The rolling surface of the first and/or second supporting wheel 11 , 12 is preferabl/ as smooth a≤ possible so as to define as accurately as possible a reference surface. The first and/or second supporting wheel 11 , 12 is preferabl/ mainly made of metal, other options are possible such as plastic, wood, etc

An alternative preferred embodiment is shown in Figures

8, 11 , 12 and 14. In this embodiment the first and second supporting wheel 11 , 12 have a relatively small contact area with the floor and extend over a preferabl/ as limited as possible contact surface to further reduce the risk that local irregularities influence the measurement too much Narrow measuring wheels a so push away loose local irregularities when driving from the contact section e'long the measuring direction which makes the measurement more accurate These supporting wheels 11 , 12 may also include several sub- wheels, n this case three so as to allow a more simple structure of the supportirg wheels 1 1 , 12.

Thte first and/or second supporting wheel 11 , 12 is preferably mainly made of metal, preferably hardened metal, other options are possible such as plastic, wood, etc

TNe second axle 14 is set up rotatably with respect to the first axle 13 around a rotation axis 15 substantially perpendicular to the first axle 13 rs shown in Figure 1. Such an assembly allows for at least a fourth support point 19 on which the support part 10 can be supported, substantially increasing the stability of the measunng apparatus 1. More preferably, and as shown in Figure 1 , the rotation axis 15 is mounted against the first axis 13 in such a way that the rotational axis crosses mainly the middle of the first main axle 13. This is not necessary for the present invention and rotation axis 15 can be o-nitted, as in the embodiment shown in Figure 8

The various support points 16, 17, 18, 19 do not need to have a f xed location abng the width of the support section 10 and can also move relative to the support section 10 when moving the measuring device 1 along th.» direction of measurement 3, It is possible that when moving the measurement apparatus- 1 along the measuring direction 3, the support points 16, 17, 18, 19 move along the contact width of the first and second supporting wheel 11 12. The support points will always be located with the highest points of the floor over the contact width of the respective supporting wheel 11 , 12 with the -loor and will rrove corresponding to irregularities in the structure of the floor along the corltact width of the supporting wheel 11 , 12 Such a support from the supporr section 10 would, according to the expenence of the inventor, have an averaging effect on the structure of the floor which defines a reference surface leadmg to a sufficiently accurate measurement of the flatness of the floor as a result In the embodiment shown in Figure 8, the support points 16, 17, 13 and possibly if present, 19 may jump between the sub-wheels of the supposing wheels 1 1 12

The measuring element 5 is provided to measure a difference* over a measuring width 4 between the reference surface and the floor along the direction of measurement 3 The sensing element 5 scans the measuring wtdth 4 wh»>e generating a measuring signal according to the difference between the rsference surface and the floor The measunng width 4 corresponds substantia^ to the contact width of a vehicle wheel and walks across th-3 measuremen' direction 3

In the context of the present patent application is a vehicle wheel a wheel ^■ suitable for supporting a vehicle With vehicle in the context cf the present patent application reference is made to a vehicle that can for example be us&d in warehouses to store loads a great heights, as explained above Such vehicles are for example fork-lift trucks Such vehicle wheels h ave a contact width, i e the width of the contact surface of the vehicle wheel wiih the floor of at least 2 cm, preferably between 2cm and 4cm, more preferabl/ at least 4cm, Tiore preferably between 4 cm and 24 cm, with further preference between 6cm and 20cm and most preferably 15cm The measunng width is therefore at leiast 2 cm, preferably between 2cm and 4cm, more preferabl/ at least 4cm, more preferably between 24 cm and 4 cm, with further preference between 6crr and 20cm and most preferably 15cm

The differences between the reference surface and the floor meεsured by the measuring apparatus 1 are preferably between 5μm and 5mm anc more preferably between 0 01 mm and 1mm

Thfe measunng element 5 shown in Figures 1 and 8 includes .a sensing element 6 provided to move up and/or down relative to the reference part 2, when tie measuπng apparatus moves along the direction of measurement 3 according to the difference between the reference surface and the floor This is not necessary for the invention and the measuπng element 5 may also comprise alternative means to measure the difference between the reference surface and the floor, such as optical, e g laser, acoustic, etc To scan the measυnng width, for example, a measuring beam is emitted by an optical sensor, a laser, air an acoustic sensor and moved along the measunng width

The up and/or downward movement of the sensing element 6 when moving the measuπng direction 3 corresponds preferably to the upwa ^r d and/or downward movement, which a vehicle wheel of the vehicle which is actually moving on the floor, experiences, such as a fork-lift trucK in a warehouse, where the vehicle wheel of the vehicle 3 moves along the direction of measurement on the floor Such an arrangement allows the measurement of the flatness of the floor to be more representative for the actual application

The sensing element 6 is preferably mounted on the measuπn9 apparatus 1 *n such a way that it essentially moves independently relative to the rest of the measunng device 1 , with more preference relative to the refer€ nee part 2

To measure the up and/or downward movement of the sensing element 6, measurement means 7 are provided The measurement means 7 generate a signal depending on the size of the upward and/or downward movement ctf the sensing element 6 relative to the reference surface The measurement means 7 are not necessary for the invention and can be determined by the person skilled in the art and may include acoustic sensors, motion sensorr, etc but are preferably optical sensors, such as a laser, as shown in the Tigures The inventor has found that such a remote sensor aWows a high accuracy of measurement of the difference between the reference surface and the floor More preferably the surface of sensing element is adapted to the measunng means 7 so as to obtain as accurate measurement results as possible of the difference between the reference surface s>nd the floor Tb this end the surface of sensing element on which the optical measuring means 7 shine in order to determine the difference between the reference surface and the floor, is preferably executed as smooth as possible.

Tho measuring means 7 are preferably mounted above the sens ng element 6 and more preferably firmly mounted relative to the reference plane, and more preferably firmly mounted relative to the reference part 2 OtSher configurations can be determined by the person skilled in the art In the measuring apparatus 1 shown in Figures 7, the measurement means are for example directly above the sensing element 7 and rigidly fixed to the reference part 2, especially down towards the first axis 13.

Figure 1 shows further that the sensing element 6 includes a contact portion 8 with a contact length essentially equal to the contact width The contact portion 8 is provided to contact, depending on the flatness of the floor, over substantially the entire length, the floor To this end, the contact length of the contact portion 8 is preferably straight as shown in the figures ^" he contact portion 8 is provided to contact, when moving the measurenent apparatus 1 along the measunng direction at least partially the floor and :o move the sensing element up and/or down while in dependence on the difference between the reference surface and the floor

When moving along the measuring direction 3 of the apparatus 1 , the contact portion 8 will contact at least one point the floor and this over possibly its entire length Possibly, the contact portion 8 also contacts multiple points of the floor In practice, the highest points of the floor will contact the contact part β and the place where the floor contacts the contact part 8 wil vary along the length of the contact part depending on where the floor is th« highest

Figjre 8 shows further that the sensing element 6 includes a contact portidn 8 that is provided to contact through two contact points se up in the measuring width of the floor, The contact portion 8 is provided to contact when moving the measuring apparatus 1 along the measuring direction at least partially the floor and thereby move the sensing element up and/or down in dependence of the differences between the reference surface and thp floor Although the contact portion 8 shown in the figures mainly comprises at least one axle 24, the measurement axle 24, mounted round measuring wheel 9, there are other possible executions for the contact part 8 T ie contact portion 8 for example, can be provided for sliding across the floor and/or shifting when moving the measurement apparatus 1 along the direction of measurement 3

The measuring wheel 9 of the contact portion 8 shown in Figures ' to 7 extends mainly along the entire measunng width 4 so that the contact width of the measuring wheel 9 essentially corresponds to the measuring width 4 Although the measunng wheel 9 can essentially be built of a single measuring wheel 9, the measuring wheel 9 shown in the figures consists of several sub-wheels mounted on an axis so as to simplify the construction of the measuring wheel 9 These wheels are preferably as close to each other as possible so that the total contact width of the wheel portion substantially corresponds to the contact width of a vehicle wheel

In !=ase of the measuring wheel 9 of the contact portion 8 shown in the embodiment shown in Figures 8 to 14, the contact portion is provided through three, with further preference exactly three, contact points, with the extreme contact points lined up on the measunng width, contacting the floor

Preferably the measunng wheel 9, or the vanous sub- wheels which form the measuring wheel 9, are mainly made of metal This is not necessary for the invention and can further be determined by the person skilled in the art The use of metal for the measuring wheels 9 however, has the advantage that the wheels are durable and can be used for different surfaces

As shown in the figures the width of the first and second axle 13, 14 is also substantially equal to the measuring width 4 and more preferably the width of the first and second supporting wheel 11 12

Tho first 13, second axle 14 and/or the measurement axle 24, if present, are preferably at a distance of substantially 50mm or 50mm, to each other, measured along the direction of measurement The inventor has found that such a distance between the first 13, second 14 and/or measurement axis 24 fulher increases the accuracy of measurement

The measuring wheel 9 of the contact portion 8 shown in the figures is connected to the first axis 13 of the reference to section 2 in order to accompany the upward and/or downward movement of the contact portion 8 In Figures 1 fo 7 this would be done by connecting the respective extremities of the axis of the measuring wheel 9 with the respective extremities of the first axis 13 by connections 20, 21 In Figures 8 to 14 this would be done by connecting the respective extremities of the axis of the measunng wheel 9 wrth the -espectrve extremities of the second axis 14 by connections 20, 21 Such a connection allows for only a substantially up and down movement in such dinensioning as the rotation around the second axis 14 through connections 20, 21 , given that the up and down movement is relatively small compared with the radius the rotary motion, is essentially equal to the length of the connections 20, 21.

In the embodiment shown in Figures 1 to 7, the downward movement df the sensing element 6, i e the movement of the sensing element 6 away from the measurement means 7 For the measunng apparatus 1 of the figures, the downward movement of the sensing element is for example limited by providing pegs 22, 23 holding the connection between the axis of the measuring wheel 9 and the first axis 13 after the sensing element 6 has earned out a certain downward motion When lifting up the measuring apparatus 1 ithis has the effect that the sensing element 7 is to lie adjacent to the reference part 2, whereby the connections 20, 21 between the axis of the measunng wheel 9 and the first axis 13 are resting on the pegs 22, 23

This is not necessary for the present invention and pegs 22, 23 may also be omifed as shown in Figures 8 to 14

For the measuring wheel 9 of the contact portion 8 shown IΓ Figures 1 to 14, contact points are provided with the contact portion to substantially or even fully support it when moving the measurement apparatus along the measuring direction in order to further increase the accuracy of the measurement

The difference between the reference surface and the floor is shown using tie measuring apparatus 1 shown in the figures, preferably determined b|/ setting up the measuring apparatus 1 on the floor in such a wiy that the measuring element 5 can measure the difference between the reference surface. Next, the measuring device 1 is moved along the measuring direction 3, To use the measuring apparatus 1 , to measure the difference between the reference surface and the floor, the difference between the reference surface and the floor is measured either on certain distances, for example, periodically or continuously for example, etc.